SNAP25 immunoreactivity occurs in horizontal cell tips at rod and cone terminals at the ultrastructural level. Preembedding immunoelectron micrographs of SNAP25 (SySy cl. 71.1) immunoreactivity at (A) cone and (B,C) rod photoreceptor terminals showed dark DAB reaction product in the lateral elements at these ribbon synapses, indicating localization of SNAP25 to horizontal cell tips. The DAB reaction product was silver-intensified and gold-toned, such that the appearance is of a fine granular nature. H, horizontal cell lateral element; B, bipolar cell process; arrowheads, synaptic ribbons. Scale bar = 0.2 μm in A–C.